Apparatus for exploring for ore



XR laama-l 4 l v 3C?- 13, 1931( L.-B.s1.xcHTER 'i 1,826,961 f APPARATUS n ExPLonma Fog ons j Filed sept. 7. 192B 2 sheets-sneu 1 {Illlllll'lllldo High* l TJ j f fami] @lm/2721;'

Oct. 13, 1931,v 'L B. sucHTER 1,325,951

AYPARATUS von ExPLoRING Fon ons 'Y' Filed sept. v. 192e 2 sheets-snm 2 l v wauwau( sul C- l i muren amies Perser orricn l l LOUIS Rmmvo? mm3?, IBGONsm Application filed Septemhgern?, 1923. Eede! Eo. 304,#9.

The resent invention relates to apparatus at the surface thereof, Said electrodes are v for exp @ring for ore, space-d apart at equal distances indicated bv More particularly, the present invention the letter a. Electrodes A and B are cori'- relates to the detection of conducting ore neet together throu hacircuit includin a 5 bodies through the; use of exploring means source of E. M. F. indicated by the letter 55 v n l disposed within a drill hole or the like. The` and the current measuring instrument F. Y'

method comprising the 'present invention is in Let it be assumed that current ows into the 5 y l essence one of determining the effective or ground at electrode A and out at B, andlet A mean electrical conductivity ofthe material the measured total current be i Let the po l 0 pierced by or located in the vicinity of a dril tentiai di'erence, E, between electrodes C and e0 hole. v `D be measured. Knowledge of the current vAn object of the present invention is to l',the dropEand the geometrical relationship provide an effective apparatus whereby secof the. four electrodes A, B, C and D is su-y 'l M tions of the earth maybe explored for buried cient to determine the electrical conductivity ore.

A. further object is to provide an apparatus the example shown, having equi-spacing of for effectively explorin the neighborhood of the four electrodes, the computation of the rea drill hole or. the like or conducting ore. sistivity is simple, as follows: Y

Further objects will appear as the deserip- Wnere 7*., is the radius of the electrodes A 20 tion proceeds.

Beferringtothe drawingsspacing between electrodes; e9 and -qao the Figure l is a schematic diagram submitted potentials of the surfaces of said hemifor the purpose of describing the present inspheres; the conductivity of the surr0undvention; mg medium; qc the potential at point. C; 4u 2 5 Figure la is a modified schematic diagram the potential at point D; and 75' submitted for the purpose of indicating 64,

another arrangement of electrodes;

Figure 2 is a schematic diagram showing a Y 3 preferred electric circuit `which may be used the pontial gradient: l

f2 I; i .f2 V E'- d a baza) (dla 2a o {1)} ca Also= the current leaving the electrode B is in the practice of the resentinvention; Figure 3 is a. viewpi lustrating the method 35 comprising the 'present invention; 11:21.14 vkls.l -85 Figure is a view illustrating an exploring ff unit which may be used in the practice of the At the Surface of the electrode present invention; o ligure is a modified :forml of exploring di is, 4:1'9 Y mii; e' n1 d 1 a "n r2 lgure snows, on ane ar e scae a. etail of the constructionshowrgi in Figiue 5'; (2l Thus 5:2'177 ofv and H fr 1 a 2 415 Figure 7 shows another modification ot' the am om an i 95 exploring unit. i

igure 1 illustrates a well known method k j- 2mg of measuring earth resistivity at the surface.

The letters A, C, D and :B indicate electrodes, The above example is given for the urpose f o having eiectrical connection with the earth of illustrating the so-called four-e ectrode 10. 'f

1,32%,9515l p f y' i of the earth at the points being tasted. In 65 l and B considered as small hemispheres; a the 79 i 12 A. i I 1,826,961 j p method. Full ex lanation of such methods' describedin the following references:

(l) Results of Earth Resistivity Survey near Watheroo, Australia, Terrestrial Magnetism Vol. 32, #2, p. 49; 15 (2) arth Resistivity Measurements in the Copper Country, Michigan, W. J. Rooney, Terrestrial L agnctism, Vol. 32, .#3, page 97 and (3) Certain applications of the Surface Pot-entialqlvlethod. lVarren Weaver. Technical Publication #121. Am. Inst. of Mining and Metallurgical Engineers.

Figure la illustrates an arrangement having the electrode C disposed between the electrodes A and B and with the electrode D outside of said electrodes A and B, spacings between the electrodes being unequal. The arrangement shown in Figure 1a is illustrated to show that the invention is not limited 3o to the arrangement shown in Figurel 1, though the arrangement shown in Figure 1 will m general be preferred.

The present'invention carries forward the teachings of the references above referred to and contemplates the exploration of earth resistivity in the neighborhood of a drill hole or similar hole extending down into the earth.

The present invention contemplates the use of an exploring member or means carrying 40 four electrodes adapted to have electrical contact with the wall of the hole referred to. Such contact with the. .wall of the hole may usually be made through the water in the hole, or may be made through mechanical contact means, suchas illustrated in the ac companying drawings. The test member is lowered down the hole a short distance at a time, land the current and voltage drops measured at each station. In order to avoid 5o polarization potentials, it is preferred to use a commutator and reverse the current at intez-vals, which may be about ten per second. If referred, special nonpolar1zing-elec tro es may be used, as for example, those using a copper sulphate solution in a porous cup.

At present, in diamond drilling, the core sample obtained is from an inch to several inches in diameter, and in churn drilling, the

' 60 sludge obtained represents a hole about six inches in diameter. A drill hole, however, may pass within a few feet of an ore deposit and give no indication of its presence. Because the small sam' les referred to may easily 5 fail to represent adequately' the true condiso-called fourtion of the zone surrounding said drill holes, many attempts have been been made to explore the -wa ls ofthe drill holes radially for some distance. In this connection, reference may be had to the United States Patent No. 1,092,065 to Loewy and the United States Patent No. 1,652,227 to Zuschlag.

The present inventionl has decided ractical advantages over any of the metho above referred to and affords an economical and reliable means of ascertaining the electrical conductivity of a zone located at any desired and known depth down a hole. Moreover, the size of the zone whose resistivity is being measured can be' readily altered to suit 80 the needs o f the particular exploration.

Referring to Figure 2, four electrodes are indicated by the numerals 1, 2, 3 and 4, electrodes 1 and 4 being current electrodes and electrodes 2 and 3 being potential electrodes. BS The numeral 10 indicates a source of directv current E. M. F., such as a battery. The numeral 9 indicates a double rotary commutator and the numeral 15 .indicates an automatic switch adapted to carry current from 9G the battery 10 to said commutator 9. Said current passes through the known resistance 13 having the taps 16, which taps communicate, by means of a selector switch 12, with one pole of a double pole double throw switch '95 11. AF rom the known resistance 13, a circuit extends Vto the elect-rode 1. The return circuit passes from the electrode 4 to the commutator 9 and thence to the battery 10. The current passing between electrodes 1 and 4 '100 'is measured after commutation by means of theknown resistance 13 in the following-way.

The double throw switch 11 when thrown to the left communicates with a circuit across f the adjustable known resistance 13. The potential across this resistance is measured by means or' the tentiometer 17. This potentiometer is ad3ustable in range by means of the selector switch 14, which communicates with the terminals 5, 6,7 and 8 of a series battery 14a in the potentiometer circuit. By

changing the volta e impressed upon the potentiometer, its sc e value is correspondingly changed. The current flow through the known resistance 13 is then given by Ohms law. In this way the true current ilow between electrodes 1 and 4 is measured. It is to be noted that any errors due to leakage of current in the commutator 9 are avoided by making the measurement on the rectified curf rent, whereby accuracy is increased. In or- :der to measure the potential differences between electrodes 2 and 3, the double throw Idouble pole switch 11 is thrown to the right ferent pointa, to wit-across the known resis'v IM I Uve, 

